Turbocharged engines are configured to compress ambient air entering the engine in order to increase power. A wastegate may control the amount of exhaust energy provided to the turbine of a turbocharger, thereby affecting boost pressure. Changes in wastegate position affect the exhaust pressure, which in turn affect engine breathing. Because of a lack of low-cost, reliable exhaust manifold pressure sensors, the exhaust pressure is often estimated in an engine controller to assist the speed-density calculations for estimating engine flow.
Typically, the exhaust pressure is estimated based in part on wastegate position. Traditional pneumatic wastegates lack position measurement, and thus wastegate position may be estimated using a force balance between the pneumatic, the spring, and the exhaust forces. However, the inventors herein have recognized that such wastegate position estimation may result in significant variability in the exhaust pressure estimation, leading to inaccurate engine air flow determinations.
Accordingly, a method is provided to at least partly address the above issues. In one embodiment, a method for an engine comprises adjusting an engine operating parameter based on exhaust pressure, the exhaust pressure estimated based on wastegate actuator motor current.
In this way, exhaust pressure may be estimated from the amount of current drawn by the motor of an electrical wastegate actuator. The current of the wastegate actuator motor may be proportional to the exhaust forces acting on the wastegate, and thus the motor current may provide an accurate mechanism for estimating the exhaust pressure and thus the engine breathing.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.